x2. If the terrain is giving you that elevation, it is often times best to keep the blind on/near to the ground as it is easier and quieter to sneak into and out of when the need arises. If the placement requires some elevation, the higher the better... to an extent. In our mesquite country, a 10' to 15' tower is usually sufficient.

+1 on it depends. This season I was a bit late to the stand a couple times. One time scared the deer away when the stand moved as I climbed the latter, next hunt I sat under the stand (behind some brush) because I saw the deer were already feeding in front of the stand, final hunt I made it up the stand about 3 minutes before the deer showed up. That said, elevated stands let you see behind bushes, plus to some degree are slightly safer because you are shooting down (gives you a little sense of security if you are around other hunters if everyone is elevated) - I say slightly because falls probably cause more problems than the elevation helps.